1. Field of the Invention
The invention relates generally to crop harvesting combines and more particularly to an automatic control of the power drive to the feeder of a combine.
2. Prior Art
The ingestion of a rock or an unusually large slug of crop material can damage the crop feeder or threshing mechanism of a combine. Moreover, a disruption of the material flow through the feeder can cause the material to build up at the feeder throat which can damage components of the crop harvesting header. The typical crop feeder includes a slip clutch in the power drive train operative to stop power drive to the feeder when the feeder is jammed with crop material or a foreign object. Slip clutches however, are subject to wear in normal use and require adjustment. Moreover, the slip clutch can be damaged through excessive slippage due to an undetected stoppage of the feeder.
U.S. Pat. No. 3,805,798 addresses one aspect of machine protection wherein the presence of rocks is detected and the feeder drive is interrupted. The passage of rocks or other objects mixed with the crop material induces a vibration in the header. An electronic detection device senses the vibration and stops the drive to the header and feeder. However, the system of this patent is effective only as a rock detector since the vibrations induced by crop material alone have low frequencies producing voltages which are filtered out. Accordingly, this system would appear to be ineffective to stop feeder drive in response to a slug or build up of crop material per se.
U.S. Pat. No. 2,749,696 shows a mechanical system for stopping power drive to a header and feed rake if the cylinder speed is reduced because of crop jamming therein. A centrifugal clutch 23 disengages drive to the sickle, header and feed rake when the speed of the cylinder allows the weight 49 in the clutch to move inwardly against centrifugal force. The drive disengaging speed of the cylinder can be selected by moving the weights to the various positions on the respective supporting arms 45.
U.S. Pat. Nos. 3,897,677 and 3,910,286 relate to threshing systems wherein the speed of the threshing cylinder is monitored or controlled. In both of these patents the concern is with jamming of the threshing cylinder. In very general terms, these patents show circuits which produce warnings or effect "controls". Neither of these patents is concerned with control of a feeder drive.